EARTH-MASON CATERPILLARS, 181 



first clears away the particles of earth and sand by placing 

 them on its broad trapezoidal head, and carrying the load 

 in this manner beyond the area of the excavation. AVhen 

 it gets deeper down, it climbs gradually up to the surface 

 with similar loads by means of the tubercles on its back, 

 above described. This process is a work of considerable 

 time and difficulty, and in carrying its loads the insect has 

 often to rest by the way to recover strength for a renewed 

 exertion. Not unfrequently, it finds the soil so ill adapted 

 to its operations, that it abandons the task altogether, and 

 begins anew in another situation. A\ hen it has succeeded 

 in forming a complete den, it fixes itself at the entrance by 

 the hooks of its tubercles, which are admirably adapted for 

 the purpose, forming a fulcrum or support, while the broad 

 plate on the top of the head exactly fits the aperture of the 

 excavation, and is on a level with the soil. In this position 

 the grub remains immovable, with jaws expanded, and ready 

 to seize and devour every insect which may wander Avithin 

 its reach, particularly the smaller beetles; and its voracity 

 is so great, that it does not spare even its own species. It 

 precipitates its prey into the excavation, and in case of 

 danger it retires to the bottom of its den, a circumstance 

 which renders it not a little difficult to discover the grub. 

 The method adopted l)y the French naturalists was to 

 introduce a straw or pliant twig into the hole, while they 

 dug away, l^y degrees and with great care, the earth aroinid 

 it, and usually found the grub at the bottom of the cell, 

 resting in a zig-zag position like one of the caterpillars of 

 the geometric moths. 



When it is about to undergo its transformation into a 

 pupa, it carefully closes the mouth of the den, and retires 

 to the bottom in security. 



It does not appear that the grub of the genus Cincin- 

 dela uses the excavation just described for the purpose of 

 a trap or pitfall, any further than that it can more efi"ec- 

 tually secure its prey by tumbling them down ^into it ; 

 but there are other species of grubs which construct pit- 

 falls for the express purpose of traps. J\mong these is 

 the larva of a fly {Rhagio vermileo), not unlike the common 



